Devices for the continuous ultrasonic processing of a material web are sufficiently known. At these devices, the ultrasonic oscillating unit usually comprises a converter, often an electro-acoustic transducer, at which a sonotrode is arranged via an amplitude transformation part, also called booster. But, there exist also embodiments wherein the sonotrode is connected directly to the converter. At such ultrasonic oscillating units, either the oscillating module is beared in a converter housing or the amplitude transformation part is beared by a retaining ring or the sonotrode is beared in a seating. These bearings are arranged always at or at least near the oscillation nodes of the ultrasonic oscillation. The sonotrode of the oscillating unit is arranged opposite to a counter tool. At the ultrasonic welding of web material, the counter tool consists of a roll having an even or an uneven circumferential contour or welding contour. It is also known to provide a rotatable sonotrode, for example in the form of a roll. In different embodiments, this sonotrode roll comprises the converter. Further, the sonotrode roll is arranged rotatably with respect to a counter tool, for example an anvil. The rotatable sonotrode roll and the counter tool perform a relative movement with respect to each other so that a gap between both is adjustable. Further, the rotatable sonotrode roll has an even or an uneven circumferential contour or welding contour.
For operating an electro-acoustic transducer (converter having a piezo-ceramic) with its parallel or ultrasonic resonance frequency, which is usually a predetermined frequency in the range of 18 kHz and 60 kHz, a special electronic power supply, an ultrasonic generator, is required. The power supply of a piezo-electronic transducer which is provided with a sonotrode must be able to feed it with its resonance frequency. Such a combination of transducer and sonotrode is mainly used for welding of thermoplastic parts, at which a power of several hundred watts up to some kilowatts is required for time intervals ranging from several milliseconds up to a continuous load. These known ultrasonic generators control or regulate only the electro-acoustic transducer.
For adjustment of an ideal welding and/or cutting clearance height between the sonotrode and the counter tool, the ultrasonic oscillating unit is driven for example by means of a pneumatic drive against a mechanical stop and fixedly positioned in this manner with respect to the counter tool. Here, it is disadvantageous that the ultrasonic oscillating unit cannot react to variations in the thickness of the material to be welded. This fixed bearing of the sonotrode is for example described in DE 195 81 256 B4.
There are also known devices wherein the ultrasonic oscillating unit is blocked via an electromotive drive (for example step motor or servomotor).
In DE 195 26 354 C1, a sensor detects the distance between the sonotrode and the counter tool. A respective signal of the sensor is then transmitted to an external controlling and regulating device. Depending on this sensor signal, a change of the distance between the sonotrode and the counter tool is controlled. In DE 10 2006 054 760 A1, a drive moves the sonotrode in the direction of the counter tool or the counter tool is moved in the direction of the sonotrode. A sensor detects the state data of the drive at its input or its output. Depending on these state data detected by the sensor, the distance between sonotrode and counter tool is changed. In DE 197 53 740 C1, a force sensor detects the pressure force of the sonotrode in the direction of the counter tool. Depending on this detected pressure force, a signal is produced by the sensor and transmitted to an external controlling or regulating device. This controlling or regulating device outputs then a respective control signal based on which the distance between sonotrode and counter tool is adjusted.
In case the material web is now guided through the welding or cutting clearance or gap, than a reaction force acts on the sonotrode generated by the material web as well as the welding force. Especially at high and/or varying welding forces, at high web speeds, at changing thicknesses of the web and at specific contours of the rolls, this reaction force leads thereto that the sonotrode gives way to the material web, i.e. the sonotrode is moved away from the counter tool. The reaction force of the web material is especially high if the roll comprises so-called transverse seams or transverse seam-like contours, i.e. an uneven circumferential contour. These are usually contours extending transversely to the rotation direction of the roll, i.e. the welding does not occur two dimensional but only on these contours (elevations). This is usually used to cut the produced single products out of the material web in a subsequent process step. In practice, it has been shown that such contours are difficult to be weld with consistent quality. As the reaction force of the web material is stronger than the blocking force, a yielding or giving way movement occurs due to bearing and clearance in the driving components of the ultrasonic oscillating unit and the gap is opened to such an extent that the following seam does not have a suitable strength. Accordingly, especially at the following seam, the welding result is not satisfying.
DE 44 00 210 A1 describes a method for physically correctly controlling the frequency and power output of a digital generator, especially for an ultrasonic welding process, as well as a reduction of the effort at the dimensionally correct manufacturing of ultrasonic transducers, amplitude transformers and sonotrodes. The method, which is performed by means of a digital control unit, compensates not only the spread of the resonance frequency in a wide range but it is also able to level displacements of the resonance point during the welding process due to temperature or pressure changes. Power fluctuations caused by fluctuations of the supply voltage or the pressure are detected and compensated by the software. The software registers the total process of inline-machines, adapts its parameters and monitors the total cycle. The sequence of the individual processes like parameter detection of the transducers system in idle state, detection of the parameters under pressure, supplying energy as gently as possible for the acoustical and electronic components, identification of trends of important system parameters and exceeding of predetermined threshold values are dealt with by the software. The software automatically detects the physically correct control and regulating parameters and therefore ensures an optimal efficiency factor during the transformation of electrical energy in ultrasonic energy.
DE 100 09 174 A1 describes an ultrasonic processing device which is operated via an external controlling and regulating device. The external controlling and regulating device receives a signal from the ultrasonic generator which characterizes the output signal of the generator. For regulating the output power of the generator, the pressing force or the amplitude of the sonotrode is adapted via the controlling and regulating device. Due to the variation of the amplitude of the sonotrode, changes of the output power of the generator are readily detectable and reaction times of the ultrasonic oscillating unit in the range of 5 to 10 ms result. If the pressing force of the sonotrode is varied via the control of a valve, reaction times in the range of 50 to 700 ms are achieved.
It is an object of at least some embodiments of the present innovations to improve the operation of known ultrasonic processing devices to the effect that it can react quickly and flexibly to a change of the operating conditions of the ultrasonic processing device so that the processing result of the ultrasonic processing device is guaranteed.